WASHINGTON, Nov 14 (Reuters) - As President Barack Obama faces a decision on whether to approve the Alberta-to-Texas Keystone XL pipeline, a study said Canadian oil sands release more planet-warming gases compared to other crudes than originally thought.

Oil sands refined in the United States released 9 percent more greenhouse gases last year than the average of other crudes processed in the country, according to the study released Wednesday by IHS CERA, an energy research group.

In 2010, the group estimated that the emissions from oil sands refined in the United States were only 6 percent higher than those from other crudes.

IHS CERA analyzed data from government, academic and industry sources to that conclude oil sands were more carbon intensive than thought two years ago.

Many environmentalists oppose oil sands crude projects because they believe the fuel is higher in emissions.

Still, IHS CERA played down the findings in the updated report. When it comes to emissions, oil sands crude is still in the league of many crude oils refined in the United States including petroleum from Venezuela, Nigeria, Iraq and heavy oil from California, the group said.

"Although the numbers have shifted slightly ... the relative position of the oil sands compared to all the other sources of crude hasn't changed much," said IHS CERA director Jackie Forrest, an author of the report called "Oil Sands, Greenhouse Gases, and U.S. Oil Supply: Getting the Numbers Right -- 2012 Update."

Canada's energy sector is seeking new markets for its oil sands crude, with such projects as TransCanada Corp's Keystone XL pipeline to Texas and Enbridge Inc's Northern Gateway pipeline to Canada's Pacific Coast.

Obama blocked the Keystone XL in January, citing environmental concerns about the project in Nebraska. Obama will likely decide on the project, which supporters say will offer thousands of jobs, early in his second term.

Ahead of Obama's decision, green groups hope to persuade the administration that stopping the Keystone XL could reduce emissions by keeping some Canadian crude in the ground.

The Natural Resources Defense Council, an environmental group, has said life cycle emissions of oil sands are 8 to 37 percent higher than other crudes processed in the United States.

Responding to the IHS Cera report Bill McKibben, an author and environmental activist, called "tar sands fuel is the dirtiest fuel on Earth." His group plans to protest at the White House on Sunday about climate and Keystone XL.

Oil sands supporters say even if Keystone XL is stopped the Canadian petroleum will eventually be sent to the United States in other pipelines or get sent to other buyers such as China, making the "keep it underground" argument moot.

One supporter said the IHS CERA report simply reflected more accurate data now available.

Greg Stringham, vice president of the Canadian Association of Petroleum Producers, the industry's main lobby group, said he is not alarmed by the higher average.

"We see it as being a similar range," compared to the earlier study, Stringham said. "But it does show that we need to push on the technology side to make sure that we continue to drive down to our objective to get that number smaller," he said.

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